Dual Drug-Loaded Coaxial Nanofiber Dressings for the Treatment of Diabetic Foot Ulcer.

Introduction: Diabetes mellitus is frequently associated with foot ulcers, which pose significant health risks and complications. Impaired wound healing in diabetic patients is attributed to multiple factors, including hyperglycemia, neuropathy, chronic inflammation, oxidative damage, and decreased vascularization. Rationale: To address these challenges, this project aims to develop bioactive, fast-dissolving nanofiber dressings composed of polyvinylpyrrolidone loaded with a combination of an antibiotic (moxifloxacin or fusidic acid) and anti-inflammatory drug (pirfenidone) using electrospinning technique to prevent the bacterial growth, reduce inflammation, and expedite wound healing in diabetic wounds. Results: The fabricated drug-loaded fibers exhibited diameters of 443 ± 67 nm for moxifloxacin/pirfenidone nanofibers and 488 ± 92 nm for fusidic acid/pirfenidone nanofibers. The encapsulation efficiency, drug loading and drug release studies for the moxifloxacin/pirfenidone nanofibers were found to be 70 ± 3% and 20 ± 1 µg/mg, respectively, for moxifloxacin, and 96 ± 6% and 28 ± 2 µg/mg, respectively, for pirfenidone, with a complete release of both drugs within 24 hours, whereas the fusidic acid/pirfenidone nanofibers were found to be 95 ± 6% and 28 ± 2 µg/mg, respectively, for fusidic acid and 102 ± 5% and 30 ± 2 µg/mg, respectively, for pirfenidone, with a release rate of 66% for fusidic acid and 80%, for pirfenidone after 24 hours. The efficacy of the prepared nanofiber formulations in accelerating wound healing was evaluated using an induced diabetic rat model. All tested formulations showed an earlier complete closure of the wound compared to the controls, which was also supported by the histopathological assessment. Notably, the combination of fusidic acid and pirfenidone nanofibers demonstrated wound healing acceleration on day 8, earlier than all tested groups. Conclusion: These findings highlight the potential of the drug-loaded nanofibrous system as a promising medicated wound dressing for diabetic foot applications.

Pharmacokinetics and Organ Distribution of C-3 Alkyl Esters as Potential Antimycobacterial Prodrugs of Fusidic Acid.

Fusidic acid (FA) has previously been shown to be rapidly metabolized in rodents to its C-3 epimer, which has significantly lower antimycobacterial activity relative to FA. This was in part hypothesized to account for FA's lack of in vivo efficacy in a mouse model of tuberculosis despite potent in vitro antimycobacterial activity. In the current work, we hypothesized that C-3 alkyl ester prodrugs of FA would deliver higher levels of the drug and prevent the rapid metabolism observed upon administration of FA in its original form. Pharmacokinetic analysis of FA and its 3-ketofusidic acid metabolite as well as novel C-3 alkyl ester prodrugs of FA revealed that FA has low exposure in mice due to rapid metabolism to a species-specific metabolite, 3-epifusidic acid. The C-3 alkyl ester prodrugs showed improved absorption and tissue distribution in pharmacokinetic and organ distribution experiments. These results support the original objective of the FA C-3 ester prodrugs to improve drug concentrations and tissue distribution.

Stability kinetics of fusidic acid: Development and validation of stability indicating analytical method by employing Analytical Quality by Design approach in medicinal product(s).

A simple, rapid, accurate, reproducible and sensitive reverse phase HPLC method for the estimation of fusidic acid (FA) by means of Analytical Quality by Design (AQbD) was the aim of the present study. Initially, the vital pre-requisites for AQbD like analytical method target profile and critical analytical attributes (CAAs) like theoretical plates, tailing factor and percent assay were defined. An octadecyl silyl silica C18 column with a packing size of 5 µm was employed and the detection was performed at 235 nm using UV-detector. The separation was performed with isocratic elution employing mixture of methanol: acetonitrile (5: 95, v/v) and an aqueous phase with pH of 2.8 containing 0.1% orthophosphoric acid in the ratio of 60: 40 (v/v). Ishikawa fish-bone diagram provided the basis of the variation in CAAs with various inputs. Taguchi Design was selected as the initial screening design to select critical method parameters (CMPs) affecting method development and Central Composite Design (CCD) was further applied for systematic optimization of chromatographic method by evaluating CAAs. Crucial parameters viz. limit of detection, limit of quantification, specificity, linearity and sensitivity were employed to validate the method in accordance with the ICH guidelines. Stress degradation studies were performed and the developed method was able to successfully differentiate the degraded products from the parent drug, that too in a topical gel. In conclusion, the findings of the present study validated the utility of AQbD in the systematic design of a liquid chromatographic method with fine sensitivity for FA estimation in medicinal products.

Pharmacokinetic-pharmacodynamic modelling to investigate in vitro synergy between colistin and fusidic acid against MDR Acinetobacter baumannii.

OBJECTIVES: The potential for synergy between colistin and fusidic acid in the treatment of MDR Acinetobacter baumannii has recently been shown. The aim of this study was to perform an extensive in vitro characterization of this effect using pharmacokinetic-pharmacodynamic modelling (PKPD) of time-kill experiments in order to estimate clinical efficacy. METHODS: For six clinical strains, 312 individual time-kill experiments were performed including 113 unique pathogen-antimicrobial combinations. A wide range of concentrations (0.25-8192 mg/L for colistin and 1-8192 mg/L for fusidic acid) were explored, alone and in combination. PKPD modelling sought to quantify synergistic effects. RESULTS: A PKPD model confirmed synergy in that colistin EC50 was found to decrease by 83% in the presence of fusidic acid, and fusidic acid maximum increase in killing rate (Emax) also increased 58% in the presence of colistin. Simulations indicated, however, that at clinically achievable free concentrations, the combination may be bacteriostatic in colistin-susceptible strains, but growth inhibition probability was <20% in a colistin-resistant strain. CONCLUSIONS: Fusidic acid may be a useful agent to add to colistin in a multidrug combination for MDR Acinetobacter baumannii.

Nano-engineered lipid-polymer hybrid nanoparticles of fusidic acid: an investigative study on dermatokinetics profile and MRSA-infected burn wound model.

Staphylococcus aureus (SA) and methicillin-resistant Staphylococcus aureus (MRSA) have been a major cause of morbidity in thermally injured patients. The skin barrier gets disrupted and loss of immunity further makes burn sites an easy target for bacterial colonization. In the current study, combined potential of lipid-polymer hybrid nanoparticles (LPHNs) with fusidic acid was explored as a promising strategy toward combating resistant bacteria in burn wound infection sites. The developed systems exhibited particle size (310.56 ± 5.22 nm), zeta potential (24.3 ± 4.18 mV) and entrapment efficiency (78.56 ± 3.56%) with a spherical shape. The hybrid nanoparticles were further gelled into carbopol and demonstrated better permeation (76.53 ± 1.55%) and retention characteristics (56.41 ± 4.67%) as compared to the conventional formulation. The topical delivery of FA into the skin layers by FA-LPHN gel was found to be significantly higher (p < 0.05) compared to FA-CC. The in vivo potential was further assessed in murine burn wound model inflicted with MRSA 33591 bacterium with the determination of parameters like bacterial burden, wound contraction, morphological and histopathological examination of wounds. The bacterial count decreased drastically in FA-LPHN gel group (5.22 log CFU/mL) on day 3 with significant difference in comparison to FA-CC. The wound size reduction in FA-LPHN gel (68.70 ± 3.65%) was higher as compared to FA-CC (73.30 ± 4.23%) and control groups (83.30 ± 4.40%) on day 5. The current study presents a safe and effective formulation strategy for the treatment of MRSA-infected burn wounds by providing moist environment and prevention from bacterial infection.

Opportunities for topical antimicrobial therapy: permeation of canine skin by fusidic acid.

BACKGROUND: Staphylococcal infection of the canine epidermis and hair follicle is amongst the commonest reasons for antimicrobial prescribing in small animal veterinary practice. Topical therapy with fusidic acid (FA) is an attractive alternative to systemic therapy based on low minimum inhibitory concentrations (MICs, commonly <0.03 mg/l) documented in canine pathogenic staphylococci, including strains of MRSA and MRSP (methicillin-resistant Staphylococcus aureus and S. pseudintermedius). However, permeation of canine skin by FA has not been evaluated in detail. This study aimed to define the degree and extent of FA permeation in canine skin in vitro from two sites with different hair follicle density following application of a licensed ophthalmic formulation that shares the same vehicle as an FA-betamethasone combination product approved for dermal application in dogs. Topical FA application was modelled using skin held in Franz-type diffusion cells. Concentrations of FA in surface swabs, receptor fluid, and transverse skin sections of defined anatomical depth were determined using high-performance liquid chromatography and ultraviolet (HPLC-UV) analysis. RESULTS: The majority of FA was recovered by surface swabs after 24 h, as expected (mean ± SEM: 76.0 ± 17.0%). FA was detected within 424/470 (90%) groups of serial sections of transversely cryotomed skin containing follicular infundibula, but never in 48/48 (100%) groups of sections containing only deeper follicular structures, nor in receptor fluid, suggesting that FA does not permeate beyond the infundibulum. The FA concentration (mean ± SEM) in the most superficial 240 µm of skin was 2000 ± 815 µg/g. CONCLUSIONS: Topically applied FA can greatly exceed MICs for canine pathogenic staphylococci at the most common sites of infection. Topical FA therapy should now be evaluated using available formulations in vivo as an alternative to systemic therapy for canine superficial bacterial folliculitis.

A Randomized Study Evaluating Oral Fusidic Acid (CEM-102) in Combination With Oral Rifampin Compared With Standard-of-Care Antibiotics for Treatment of Prosthetic Joint Infections: A Newly Identified Drug-Drug Interaction.

BACKGROUND: Fusidic acid (FA) has been used for decades for bone infection, including prosthetic joint infection (PJI), often in combination with rifampin (RIF). An FA/RIF pharmacokinetic interaction has not previously been described. METHODS: In a phase 2 open-label randomized study, we evaluated oral FA/RIF vs standard-of-care (SOC) intravenous antibiotics for treatment of hip or knee PJI. Outcome assessment occurred at reimplantation (week 12) for subjects with 2-stage exchange, and after 3 or 6 months of treatment for subjects with hip or knee debride and retain strategies, respectively. RESULTS: Fourteen subjects were randomized 1:1 to FA/RIF or SOC. Pharmacokinetic profiles were obtained for 6 subjects randomized to FA/RIF. FA concentrations were lower than anticipated in all subjects during the first week of therapy, and at weeks 4 and 6, blood levels continued to decline. By week 6, FA exposures were 40%-45% lower than expected. CONCLUSIONS: The sponsor elected to terminate this study due to a clearly illustrated drug-drug interaction between FA and RIF, which lowered FA levels to a degree that could influence subject outcomes. Optimization of FA exposure if used in combination with RIF should be a topic of future research. CLINICAL TRIALS REGISTRATION: NCT01756924.

Stability-indicating RP-LC method for quantification of fusidic acid in cream

ABSTRACT Fusidic acid is an antibiotic steroid indicated for the treatment of infections caused by the genus Staphylococcus, including methicillin resistant Staphylococcus aureus strains, and other Gram-positive bacteria. In the present study, a stability-indicating reversed-phase liquid chromatography (RP-LC) method was developed and validated for the determination of fusidic acid in dermatological cream as an alternative to existing methods. Analyses were performed using a C18 column and guard column at room temperature, eluting with an isocratic mobile phase of acetonitrile and water (72:28, v/v), adjusted to pH 3.5 with acetic acid, pumped at a flow rate of 1.0 mL min-1, detection at 210 nm and 20 µL of injection volume. The forced degradation study was conducted under acidic, alkaline, neutral, photolytic, and oxidative stress conditions. The method was validated according to ICH and FDA guidelines; it was linear, precise, accurate, selective, and robust over concentrations of 5-95 µg mL-1, with detection and quantification limits of 0.43 and 1.31 μg mL-1, respectively. Therefore, we conclude that this method is suitable for quantifying fusidic acid in pharmaceutical dermatological creams and determining its stability, representing a more economical and practical alternative for routine analysis in quality control.

Injectability, microstructure and release properties of sodium fusidate-loaded apatitic cement as a local drug-delivery system.

The introduction of an antibiotic, sodium fusidate (SF), into the liquid phase of calcium carbonate-calcium phosphate (CaCO3-CaP) bone cement was evaluated, considering the effect of the liquid to powder ratio (L/P) on the composition and microstructure of the set cement and the injectability of the paste. In all cases, we obtained set cements composed mainly of biomimetic carbonated apatite analogous to bone mineral. With this study, we evi-denced a synergistic effect of the L/P ratio and SF presence on the injectability (i.e., the filter-pressing pheno-menon was suppressed) and the setting time of the SF-loaded cement paste compared to reference cement (without SF). In addition, the in vitro study of SF release, according to the European Pharmacopoeia recommendations, showed that, regardless of the L/P ratio, the cement allowed a sustained release of the antibiotic over 1month in sodium chloride isotonic solution at 37°C and pH7.4; this release is discussed considering the microstructure characteristics of SF-loaded cements (i.e., porosity, pore-size distribution) before and after the release test. Finally, modelling antibiotic release kinetics with several models indicated that the SF release was controlled by a diffusion mechanism.

Population pharmacokinetics of fusidic acid: rationale for front-loaded dosing regimens due to autoinhibition of clearance.

The objectives of this analysis were to develop a population pharmacokinetic (PK) model to describe the absorption and disposition of fusidic acid after single and multiple doses and to determine the effect of food on the rate and extent of bioavailability. Plasma PK data from three phase 1 studies (n = 75; n = 14 with and without food) in which healthy subjects received sodium fusidate (500 to 2,200 mg) as single or multiple oral doses every 8 h (q8h) or q12h for up to 7 days were modeled using S-ADAPT (MCPEM algorithm). Accumulation of fusidic acid after multiple doses was more than that predicted based on single-dose data. The PK of fusidic acid was best described using a time-dependent mixed-order absorption process, two disposition compartments, and a turnover process to describe the autoinhibition of clearance. The mean total clearance (% coefficient of variation) was 1.28 liters/h (33%) and the maximum extent of autoinhibition was 71.0%, with a 50% inhibitory concentration (IC(50)) of 46.3 mg/liter (36%). Food decreased the extent of bioavailability by 18%. As a result of the autoinhibition of clearance, steady state can be achieved earlier with dosing regimens that contain higher doses (after 8 days for 750 mg q12h and 1 day for 1,500 mg q12h on day 1 followed by 600 mg q12h versus 3 weeks for 500 mg q12h). Given that large initial doses autoinhibit the clearance of fusidic acid, this characteristic provides a basis for the administration of front-loaded dosing regimens of sodium fusidate which would allow for effective concentrations to be achieved early in therapy.

Modelling of the outcome of non-inferiority trials by integration of historical data.

The approval and differentiation of new compounds in clinical development often demands non-inferiority trials, in which the test drug is compared against a reference treatment. However, non-inferiority trials impose major operational burden with serious ethical and scientific implications for the development of new medicines. Traditional approaches make limited use of historical information on placebo and neglect inter-trial variability, relying on the constancy assumption that the control-to-placebo effect size is maintained across trials. We propose a model-based approach that overcomes such limitations and may be used as a tool to explore differentiation during clinical development. Parameter distributions are introduced which reflect the heterogeneity of trials. The method is illustrated using data from impetigo trials. Based on simulation scenarios, this Bayesian technique yields a definitive, consistent increase in the statistical power over two accepted statistical methods, allowing lower sample size requirements for the assessment of non-inferiority.

Pharmacokinetics and safety of single, multiple, and loading doses of fusidic acid in healthy subjects.

A phase 1 trial of fusidic acid (CEM-102), an oral fusidane class antibiotic under development for treatment of gram-positive acute bacterial skin and skin structure infections, evaluating pharmacokinetics and safety is described. A randomized, double-blinded, placebo-controlled, dose escalation study was conducted in healthy adult subjects in the fasting state. Plasma exposure after multiple doses was higher than for single doses, indicating accumulation. Loading doses designed to optimize pharmacodynamic effects were well tolerated and achieved near-steady state concentrations of CEM-102 at 24 h. CEM-102 was safe and generally well tolerated at all single, multiple, and loading doses administered.

Application of pharmacokinetic-pharmacodynamic modeling and the justification of a novel fusidic acid dosing regimen: raising Lazarus from the dead.

Perhaps the most crucial step in the clinical development of an antimicrobial agent is the selection of a dosing regimen. Such decisions impact not only the success of a program but also the well being of individual patients, the emergence of resistance, and society as a whole. For fusidic acid, the selection of a dosing regimen for the treatment of patients with acute bacterial skin and skin-structure infection (ABSSSI) was based on the integration of knowledge gained from human population pharmacokinetic, in vitro infection, and mathematical models. The overarching goal of these studies was to identify a dosing regimen that would maximize the probabilities of positive clinical outcomes and limit the emergence of bacterial resistance during therapy. Novel dosing regimens identified included 1500 mg twice daily on day 1 followed by 600 mg twice daily for 10-14 days, a regimen that was subsequently found to be effective in a phase 2 clinical study of patients with ABSSSI. Herein, we review the data supporting the use of this novel fusidic acid dosing regimen, which will undergo further clinical evaluation in phase 3 clinical trials.

Evaluation of the pharmacokinetics-pharmacodynamics of fusidic acid against Staphylococcus aureus and Streptococcus pyogenes using in vitro infection models: implications for dose selection.

The pharmacokinetics-pharmacodynamics (PK-PD) of fusidic acid were investigated against methicillin-resistant Staphylococcus aureus (MRSA) and Streptococcus pyogenes using in vitro infection models. Front-loaded and non-front-loaded fusidic acid dosing regimens were evaluated over 48 h using a 1-compartment infection model and over 240 h using a hollow fiber infection model (HFIM). All dosing regimens demonstrated initial decreases in bacterial density against both isolates in both in vitro models. A mechanism-based PK-PD model was developed to describe the effect of the concentration-time course of fusidic acid on the time course of MRSA in the in vitro infection model. With the use of this model and Monte Carlo simulation to evaluate the effect of different dosing regimens against MRSA, front-loaded [≥ 1200 mg every 12 h (Q12) × 2 doses followed by ≥ 600 mg Q12 h] compared to non-front-loaded (600 mg Q12 h) dosing regimens demonstrated better activity. HFIM data confirmed the effect of the front-loaded dosing regimens over 48 h and also demonstrated the suppression of growth of the total population and resistant subpopulations for MRSA over 96 and 120 h, respectively, associated with these dosing regimens.

Antimicrobial PLGA ultrafine fibers: interaction with wound bacteria.

The structure and functions of polymer nanofibers as wound dressing materials have been well investigated over the last few years. However, during the healing process, nanofibrous mats are inevitably involved in dynamic interactions with the wound environment, an aspect not explored yet. Potential active participation of ultrafine fibers as wound dressing material in a dynamic interaction with wound bacteria has been examined using three wound bacterial strains and antimicrobial fusidic acid (FA)-loaded electrospun PLGA ultrafine fibers (UFs). These were developed and characterized for morphology and in-use pharmaceutical attributes. In vitro microbiological studies showed fast bacterial colonization of UFs and formation of a dense biofilm. Interestingly, bacterial stacks on UFs resulted in a remarkable enhancement of drug release, which was associated with detrimental changes in morphology of UFs in addition to a decrease in pH of their aqueous incubation medium. In turn, UFs by allowing progressively faster release of bioactive FA eradicated planktonic bacteria and considerably suppressed biofilm. Findings point out the risk of wound reinfection and microbial resistance upon using non-medicated or inadequately medicated bioresorbable fibrous wound dressings. Equally important, data strongly draw attention to the importance of characterizing drug delivery systems and establishing material-function relationships for biomedical applications under biorelevant conditions.

Effect of sodium carboxymethylcellulose and fucidic acid on the gel characterization of polyvinylalcohol-based wound dressing.

The purpose of this study was to investigate the effect of sodium carboxymethylcellulose (Na-CMC) and fucidic acid on the gel characterization for the development of sodium fucidate-loaded wound dressing. The cross-linked hydrogel films were prepared with polyvinyl alcohol (PVA) and sodium carboxymethylcellulose (Na-CMC) using the freeze-thawing method. Their gel properties such as gel fraction, swelling, water vapor transmission test, morphology, tensile strength and thermal property were investigated. In vitro protein adsorption test and release were performed. Na-CMC decreased the gel fraction and tensile strength of the hydrogels, but increased the swelling ability, water vapor transmission rate, elasticity and porosity of hydrogels. Thus, the wound dressing developed with PVA and Na-CMC was more swellable, flexible and elastic than that with only PVA because of its cross-linking interaction with PVA. However, the drug had a negative effect on the gel properties of hydrogels but there were no significant differences. In particular, the hydrogel composed of 2.5% PVA, 1.125% Na-CMC and 0.2% drug might give an adequate level of moisture and build up the exudates on the wound area. Thus, this sodium fucidate-loaded hydrogel could be a potential candidate for wound dressing with excellent forming.

Pharmacokinetics of fusidic acid and cefepime in heart tissues: implications for a role in surgical prophylaxis.

The pharmacokinetic profiles of fusidic acid and cefepime in heart tissues were assessed in 30 patients undergoing elective valve replacement and cardiopulmonary bypass. Single doses of 1 g of fusidic acid and 2 g of cefepime were administered intravenously to two groups of 15 and 15 patients respectively upon initiation of anesthesia. Samples of serum, heart valves, myocardium, pericardium, mediastinal fat and sternum were collected within <1 hour, 1-2 h and 2-4 h after the end of drug infusion. Drug concentrations were estimated by a microbiological assay. It was found that concentrations of fusidic acid in all specimens were 20-fold higher than the MIC90s of methicillin-resistant Staphylococcus aureus and Staphylococcus epidermidis, being at such levels throughout all period of sampling. Cefepime concentrations in heart valves collected 1-2 h after drug infusion were higher than the MIC90s of multidrug-resistant Enterobacteriaceae. It is concluded that both fusidic acid and cefepime penetrated heart tissues adequately; however only fusidic acid could also accumulate in the mediastinum. These data suggest that both antibiotics may be a good alternative for prophylaxis in open heart surgery.

Development of an in vitro skin permeation model simulating atopic dermatitis skin for the evaluation of dermatological products.

Atopic dermatitis (AD) skin has a defective barrier function as indicated by increased transepidermal water loss (TEWL). In order to test potential new formulations for AD, it was our aim to develop a skin permeation model simulating AD skin by inducing barrier impairment to otherwise healthy skin simulating the barrier properties of AD skin as evaluated by TEWL measurements. Pig ear skin was mounted to Franz-type diffusion cells. Skin barrier impairment was induced by tape strippings. As the number of strips increased, higher TEWL values were obtained. By performing 25 tape strippings, the TEWL value within the range reported for involved skin of AD patients was reached. The in vitro skin permeation of fusidic acid and betamethasone-17-valerate was found to correlate with the number of tape strippings used to remove stratum corneum cell layers. A comparison of the permeability of fusidic acid and betamethasone-17-valerate from Fucicort cream to a new Fucicort Lipid formulation was studied with intact (0 strippings) and barrier-impaired skin simulating involved AD skin (25 strippings). As opposed to intact skin, no statistically significant difference through barrier-impaired skin was found for fusidic acid and betamethasone-17-valerate for the two formulations. This is in accordance with the clinical results of an international multicentre study and thus confirms the predictability of the model.

Fusidic acid viscous eyedrops--an evaluation of pharmacodynamics, pharmacokinetics and clinical use for UK optometrists.

Recent changes in UK law have allowed UK-based optometrists to sell and supply fusidic acid viscous eyedrops, providing it is in the course of their professional activity and in an emergency. Alternatively, the optometrist may access fusidic acid viscous eyedrops, for a named patient, using a written order supplied to a pharmacy. This review provides details of the legal background to these changes, examines the common causes of a bacterial conjunctivitis, examines the mechanism of action of this narrow spectrum antibiotic as a bacteriostatic agent, reviews the susceptibility of common ocular isolates of bacteria to the drug and presents details of the expected pharmacokinetics of the viscous eyedrops. From this perspective, a systematic review is provided of the clinical studies which have investigated the use of fusidic acid viscous eyedrops and their outcome. The indicated use is generally for the treatment of bacterial conjunctivitis and/or blepharoconjunctivitis, especially that caused by Staphylococcus, but not Streptococcus or Haemophilus sp. (more likely associated with concurrent nasopharyngeal infections). The usual regimen for use is twice daily for 5-10 days, depending on severity, and can initially be used more intensively (four times per day). It may also be used for the management of corneal and conjunctival abrasions and foreign body injuries, or some cases of chronic blepharitis.